In the use of a commercial or industrial light fixture, for example, of the type disclosed in U.S. Pat. Nos. 4,021,660 and 4,138,713 which issued to the assignee of the present invention, it is sometimes desirable for the fixture to be used in an environment where the air contains a gas or fumes or particles which will easily ignite. For example, the light fixture may be used in a coal mine or a petroleum refinery, or granary or chemical plant where it is highly desirable to prevent an accidental explosion within the light fixture from escaping and igniting the gas or particles within the surrounding environment. Thus it is necessary for the light fixture to provide some means for releasing an explosive gas within the light fixture to prevent cracking of the glass lens and also to extinguish any flame which develops within the fixture and attempts to escape with the pressurized gas.